Cover Crop: A Definition

Rye cover crop, Portage La Prairie, Manitoba, Canada.
Mike Grandmaison/All Canada Photos/Getty Images

A cover crop is a crop of a specific plant that is grown primarily for the benefit of the soil rather than the crop yield. Cover crops are commonly used to suppress weeds, manage soil erosion, help build and improve soil fertility and quality, and control diseases and pests. Cover crops are typically grasses or legumes but may be comprised of other green plants.

Cover Crop Benefits

Cover crops improve biodiversity by increasing the variety of species in a given area. They also can help reduce the amount of water that drains off a field, protecting waterways and downstream ecosystems from erosion. Because each root of the cover crop creates pores in the soil, cover crops help allow water to filter deep into the ground. As a result, they help conserve water in several ways.

Cover crops can help break disease cycles by reducing the amount of bacterial and fungal diseases in a soil. If you have a soil that is infested, you can plant a cover crop in that area as a means to eradicate the disease.

Cover crops are sometimes called "green manure" because they provide nutrients to the soil, much like manure does. They are also called "living mulches" because they can prevent soil erosion. A mulch is a layer of organic material, such as crop residue, left on the surface of the soil to prevent water runoff and protect the soil from the damaging effects of heavy rainfall.

Organic Gardening with Cover Crops

Cover crops are an important part of sustainable agriculture because they add fertility to the soil without chemical fertilizers via biological nitrogen fixation. They also offer a natural way to reduce soil compaction, manage soil moisture, reduce overall energy use, and provide additional forage for livestock.

Small farmers choose to grow specific cover crops based on their needs and goals and the overall requirements of the land they are working. Cover crops grown in summer are often used to fill in space during crop rotations, help amend the soil, or suppress weeds. Winter cover crops help hold soil in place over the winter and provide ground cover. They can also fix nitrogen levels in the soil.

Planting After a Cover Crop

Once a cover crop is fully grown, or the farmer wants to plant in an area the has a cover crop, the conventional technique is to mow down the cover crop and allow it to dry. After it's dry, the remaining organic matter is usually tilled into the soil. However, many progressive farmers in drought-prone areas favor a no-till method, in which the residue from the cover crop is left on the soil as a mulch layer.

Types of Cover Crops

Here are some examples of plants that have proven to be effective cover crops:

  • Rye: Also known as winter rye or cereal rye, this cover crop is often used to loosen compact soil and suppress weeds.
  • Buckwheat: Fast-growing buckwheat helps prevent erosion and suppress weeds.
  • Clover: Clover is great for fixing nitrogen in the soil, adding fertility.
  • Sorghum: This hybrid cover crop grows quickly, adds biomass, and suppresses weeds.
  • Hairy Vetch: Vetch adds nitrogen and is a good overwinter crop for northern climates.